PUPILLIDAE 



101 



GASTROCOPTA TAPPANIANA (C. B. Adams) 



Larger and more sharply conic than that of Gastrocopta 

 pentodon, the opaque white shell of Gastrocopta tappaniana 

 measures over one-sixteenth inch (2 mm.) in height. The spire 

 has an obtuse apex, the parietal 

 lamella is straight and the lower 

 palatal fold is usually not so long 

 as is that in pentodon. There are 

 usually 6 (sometimes as few as 2) 

 folds on the outer lip. The figures 

 show variations in individual shells. 



Gastrocopta tappaniana is found 

 beneath pieces of wood, logs and 

 damp debris in wet places such as 

 floodplains, moist woodlands and swamp edges, while Gastro- 

 copta pentodon prefers drier situations. It is distributed through- 

 out Illinois in about the same scattered manner as Gastrocopta 

 pentodon. 



GASTROCOPTA CORTICARIA (Say) 



Measuring less than one-eighth inch (2.5 mm.) in height, 

 the shell of Gastrocopta corticaria usually has but 2 lamellae, 

 a parietal lamella and a columellar lamella. Occasionally it 

 has another lamella, the angular, developed and 

 united with the parietal lamella. In rare indi- 

 viduals the aperture is without lamellae. The 

 shell has no folds on the outer lip, and no fold 

 at the base of the aperture. 



Gastrocopta corticaria is unique among the 

 species of this genus in having the folds and 

 lamellae very few in number. No other Gastro- 

 copta is comparable to it. 



This tree-inhabiting Gastrocopta is distrib- 

 uted throughout Illinois in a scattered manner. 

 Its habitat is on hillsides, river bluffs and wood- 

 lands where oak, elm, basswood and hickory are 

 the usual forest trees. The species corticaria, the "bark in- 

 habiter," is often observed as high as 2 feet from the ground 

 on the trunk of a tree. 



